[gradsusr] Lifted Index Formula

[Mike Manning]

Thanks Jeff I'll give that a go :)

Cheers, Mike

On 2/03/2012 2:25 AM, Jeff Duda wrote:
> You've confused the different uses of scripting functions vs. Grads 
> prompt functions.  You can only display a variable that you have 
> defined using the 'define ...' command (note the use of the quotes 
> signaling that it was defined as if you typed it in at the Grads 
> prompt).  Your use of variable = satvap(...) with satvap being a 
> script function only is causing Grads to assume variable is a script 
> variable only, not one that can be displayed.  The reason you get the 
> other error when you put the other line in quotes is because math_exp 
> is strictly a script version of the exp function that you would use in 
> the Grads command prompt.  Thus, you would want to change that line to
>
> 'es = 6.112*exp(17.67*temp/(temp+243.5))'
>
> in order to display es or define any other variables that would depend 
> on it.
>
> Jeff Duda
>
> On Thu, Mar 1, 2012 at 7:06 AM, Mike Manning <michael at bsch.au.com 
> <mailto:michael at bsch.au.com>> wrote:
>
>     Hi everyone,
>
>     I'm using data from the FNMOC model and am trying to make a function
>     that calculates Lifted Index.  I'm using bits of the code from the
>     plotskew.gs <http://plotskew.gs> code.  So far I've got the
>     temperature (celsius) and
>     dewpoint (celsius) worked out for each level.  Now I'm calculating the
>     parcel details.. I've pulled some of the functions and have just been
>     testing to make sure I'm on the right track.  If I have this code for
>     example:
>
>     'c'
>     'reinit'
>     'open gfs.00z.ctl'
>     'set t 7'
>     'set lon 135 155'
>     'set lat -31 -10'
>
>     'set lev 1000'
>     't1000mb = TMPprs-273.14'
>     'define dp1000mb =
>     t1000mb-((14.55+0.114*t1000mb)*(1-0.01*RHprs)+pow((2.5+0.007*t1000mb)*(1-0.01*RHprs),3)+(15.9+0.117*t1000mb)*pow((1-0.01*RHprs),14))'
>
>     variable = satvap2(t1000mb)
>
>     'd variable'
>
>     function satvap2(temp)
>
>     *---------------------------------------------------------------
>     * Given temp in Celsius, returns saturation vapor pressure in mb
>     *---------------------------------------------------------------
>
>     es=6.112*math_exp(17.67*temp/(temp+243.5))
>
>     return(es)
>     'quit'
>
>
>
>     it complains about an error? If I put the code in the satvap2 function
>     in single quotes it then says "math_exp" is not a variable or
>     function"?
>     I'm a little lost on how to fix this one up if it's possible.
>
>     Cheers, Mike
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>
>
>
> -- 
> Jeff Duda
> Graduate research assistant
> University of Oklahoma School of Meteorology
> Center for Analysis and Prediction of Storms
>
>
>
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